I. Field
The following description relates generally to wireless communications, and more particularly to employing fractional frequency reuse (FFR) with multiple carriers in a heterogeneous wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT,NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
Heterogeneous wireless communication systems commonly can include various types of base stations, each of which can be associated with differing cell sizes and power classes. For instance, macro cell base stations typically leverage antenna(s) installed on masts, rooftops, other existing structures, or the like. Further, macro cell base stations oftentimes have power outputs on the order of tens of watts, and can provide coverage for large areas. The femto cell base station is another class of base station that has recently emerged. Femto cell base stations are commonly designed for residential or small business environments, and can provide wireless coverage to access terminals using a wireless technology (e.g., 3GPP Universal Mobile Telecommunications System (UMTS) or Long Term Evolution (LTE), 1× Evolution-Data Optimized (1xEV-DO), . . . ) to communicate with the access terminals and an existing broadband Internet connection (e.g., digital subscriber line (DSL), cable, . . . ) for backhaul. A femto cell base station can also be referred to as a Home Node B (HNB), a femto cell, a closed subscriber group (CSG) cell, or the like. The pico cell base station is another class of base station that oftentimes is included in heterogeneous wireless communication systems. Pico cell base stations typically transmit at lower power as compared to macro cell base stations and oftentimes cover small areas (e.g., in a building, in an aircraft, . . . ). Further, pico cell base stations are oftentimes located within coverage areas of macro cell base stations. Moreover, heterogeneous wireless communication systems can include other types of base stations such as micro cell base stations or the like.
Conventional wireless communication systems oftentimes utilize one carrier for downlink operation and one carrier for uplink operation. More recently, wireless communication systems that support utilization of multiple carriers on the uplink and/or multiple carriers on the downlink have become more prevalent. Accordingly, an access terminal can transmit and/or receive data on multiple carriers. For instance, larger system bandwidths (e.g., beyond 20 MHz, . . . ) for downlink operation can be yielded by supporting carrier aggregation. Common approaches, however, can inadequately manage interference between base stations of different power classes within a multicarrier heterogeneous network deployment.